1. Field of the Invention
This invention relates to an organopolysiloxane composition which is superior in both antibacterial properties and mildew resistance and also superior in weatherability such as heat resistance and ultraviolet light resistance and may cause less change in color, used in sealing mediums and so forth.
2. Description of the Prior Art
Moisture-crosslinkable, room temperature vulcanizing (RTV) silicone rubber compositions are utilized in various fields such as sealing mediums used for construction materials and adhesives used in electric and electronic fields. In particular, deoxime (or oxime-elimination) type RTV silicone rubber compositions are put into wide use because of their good adhesion to various adherends at wet places where water is used, e.g., kitchens and bathrooms in houses and also because of their superior weatherability.
Meanwhile, an improvement of construction techniques for housing in recent years has brought about an improvement in airtightness, and the wet places where water is used in houses provide suitable habitats for microorganisms such as fungi. In particular, fungi insert their hyphae up to the interior of RTV silicone rubber, and hence it is difficult not only to wipe off them but also remove them by chemicals, often resulting in damage of visual appearance.
As a measure for solving such a problem, it is common to add mildewproofing agents mixedly into sealing mediums. Especially in the case of silicone sealing mediums, proposed as mildewproofing agents from the viewpoint of mildew resistance and safety are 2,3,5,6-tetrachloro-4-methylsulfonylpyridine (Japanese Pre-examination Patent Publication (kokai) No. 51-106158), 2-(4-thiazolyl)benzimidazole (Japanese Pre-examination Patent Publication (kokai) No. 54-127960 and N-substituted benzimidazolyl carbamate derivatives such as methylbenzimidazol-2-yl carbamate (Japanese Pre-examination Patent Publication (kokai) No. 56-38348). Silicone sealing mediums containing these mildewproofing agents, however, have a problem of yellowing caused by heating and ultraviolet rays. Hence, such mildewproofing agents have had to be added in a small amount limited to such an extent that the yellowing does not occur, so that no sufficient mildew resistance has been exhibited. In particular, deoxime type compositions making use of an unsaturated-group-containing hydrolyzable silane as a curing agent tend strongly to cause this yellowing. Accordingly, as an mildewproofing agent that can restrain the yellowing, the present inventors have proposed a triazolyl-group-containing compound, as disclosed in Japanese Pre-examination Patent Publications (kokai) No. 8-217977 and No. 9-25410.
Meanwhile, in recent years, because of the problem of toxication due to pathogenic Escherichia coli O-157 and the development and sale of antibacterial type commodities such as floorings, sanitary earthenware and so forth endowed with antibacterial properties, sealing mediums used therein have become required to be made antibacterial.
However, the above conventional sealing mediums aiming chiefly at mildewproofing do not take account of the antibacterial properties. Accordingly, the present inventors have proposed a sealing medium comprising an organic mildewproofing agent such as an N-substituted benzimidazole compound with which an inorganic antibacterial agent of a silver, tin or copper type is combined so as to be endowed with both antibacterial properties and mildew resistance, as disclosed in Japanese Pre-examination Patent Publication (kokai) No. 7-76654. This sealing medium has a sufficient mildew resistance and also satisfies the antibacterial properties to a certain extent, but has still been insufficient in view of the permanence of antibacterial properties and the restraint of yellowing.